In August, DPR prime minister admitted professional Russian soldiers were fighting in Donbas

A local field commander, Mr Zakharchenko became the “prime minister” of the self-styled “Donetsk People’s Republic” (DPR) in early August after his predecessor, Russian citizen Alexander Borodai, announced he was stepping down.

On 28 August Mr Zakharchenko admitted that thousands of Russian citizens, including many professional soldiers, were fighting alongside the separatists.

http://www.bbc.com/news/world-latin-america-27211501